linux-kernel - Re: [PATCH v8] seccomp, ptrace: add support for dumping seccomp filters

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Date:	Sun, 25 Oct 2015 16:39:43 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tycho Andersen <tycho.andersen@...onical.com>
Cc:	Kees Cook <keescook@...omium.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Will Drewry <wad@...omium.org>,
	Andy Lutomirski <luto@...capital.net>,
	Pavel Emelyanov <xemul@...allels.com>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH v8] seccomp, ptrace: add support for dumping seccomp
	filters

On 10/21, Tycho Andersen wrote:
>
> > And this leads to another question... If we expect that this interface
> > can change later, then perhaps PTRACE_SECCOMP_GET_FILTER should also
> > dump some header before copy_to_user(fprog->filter) ? Say, just
> > "unsigned long version" == 0 for now. So that we can avoid
> > PTRACE_SECCOMP_GET_FILTER_V2 in future.
>
> So this is interesting. Like Kees mentioned, the bulk of the work
> would be done by the bpf syscall. We'd still need some way to get
> access to the fd itself, which we could (ab)use
> PTRACE_SECCOMP_GET_FILTER for, by returning the fd + BPF_MAXINSNS (so
> that it doesn't conflict with length) or something like that. Or add a
> _V2 as you say. If there is some change we can make to have a nicer
> interface than fd + BPF_MAXINSNS to future proof, I'm fine with making
> it.

Can't comment, this is up to you/Kees ;)

So, just in case, let me repeat I am fine with this patch.

Oleg.

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